A problem with using load cells in weighing scales is their sensitivity to applied moments. These moments result from the non-linearities in the deflection of the load support, and from shifts of the load upon the pan. Conventional solutions to this problem generally feature three or more load cells, and the averaging of the load cell readings to cancel the effects of the moments. Another solution features the use of a balance beam mechanism and knife edge supports. Both of these solutions are complicated and expensive.
When leaf springs are used as part of the load support structure of a scale, non-linearities in the load support deflection may also introduce applied moments to the load cells, thus causing inaccuracies. In addition, the leaf springs also may exhibit a condition referred to as "oil canning". Oil canning is a localized bulging that may occur in the thin flat leaf spring material due to inconsistencies of manufacture and assembly. This bulging will also introduce errors into the weight determination.
The subject invention has provided a highly accurate weighing scale by combining a pair of twin leaf springs, and a pair of load cells. The invention, however, is not limited by the aforementioned disadvantages.